AI agents use track_set_solo to create or update resources in ReaperMCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your ReaperMCP environment.
Setting a track's solo state is a reversible modification to a project parameter. It does not delete data, execute arbitrary code, or involve financial transactions. The blast radius is minimal — misuse at worst causes unintended audio monitoring changes during a session.
From the tool's definition Solo/unsolo a track — reversibly changes the solo state of a track in REAPER
Documented attack patterns abuse exactly the kind of access track_set_solo gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and ReaperMCP, and nothing reaches the server without passing your rules. This is the rule we recommend for track_set_solo:
{
"version": "1",
"default": "deny",
"tools": {
"track_set_solo": {
"limits": [
{
"counter": "track_set_solo_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}track_set_solo stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Solo/unsolo a track. It is categorised as a Write tool in the ReaperMCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Reaper MCP server in PolicyLayer and add a rule for track_set_solo: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches ReaperMCP. Nothing to install.
track_set_solo is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the track_set_solo rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for track_set_solo. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
track_set_solo is provided by the Reaper MCP server (xdarkzx/reaper-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from ReaperMCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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